Conduit system



Oct. 13, 1931. l 1. H. HUNTER 1,827,085

CONDUIT SYSTEM Filed April 13, 1925 2 Sheets-Shem l J. H. HUNTER CONDUIT SYSTEM oct. 13, 1931,.

2 Sheets-Sham 2 Filed April 13., 1925 Patented ct. 13, 1931 UNITED 'STATESy PATENT-formen JOSEPH H. HUNTER, F DETROIT, MICHIGAN, lASSIG'N'OIR., BY ASSIGNMENTS, T0 .l GENERAL CABLECORPORATION, .A CORPORATION OF NEW JERSEY CONDUIT SYSTEM appuoauan. mea April 1s, 1925. serial No. 22,852.

The invention relates to fiexible conduit systems more particularly designed for containing electrical conductors yand the invention consists in the novel construction and method of installation as hereinafter set forth.

In the drawings:

Figure 1 is a longitudinal section through two conduit sections coupled to each other;

Figure 2 is a similar view of a modified construction; e

Figure 3 illustrates two conduit sections of different diameters screwed into engagement with each` other;

Figure 4 shows a conduit connected withA an outlet fitting; l n

Figure 5 illustrates a T-connection between conduit sections; j Figures 6 and 7 are cross sections on lines 6-6 and 7.-7 of Figure 5 Figure 8 is a section through' a junction box; v

Figure 9 is a perspective view of a conduit securing cllp;

Figures 10 and 1l are longitudinal sections showing the union of conduit sections varying considerably in diameter;

Figure 12 illustrates the connection of the conduitwith an ordinary outlet box;

Figure 13 is a section through a cross coupling for conduit sections.

.In the present state of the art one type of flexible conduit which is extensively used is formed from a spirally wound'strip of sheet metal so fashioned that the adjacent convolutions will interlock but permit of a limited relative angular movement. vSuch conduits are frequently used for enclosing electrical conductors, butare` not generally used for forming permanently installed conduit systenis connected with junction boxes and other fittings. One reason for this is that it has been found difiicult to form a satisfactory mechanical joint between lsuch conduits and other fittings.

The present invention involves the novel idea of utilizing the spiral winding primarily designed fox` flexibility, as a means for joining conduit sections with each other or with other fittings. Thus a permanent conduit system may be readily installed with less labor than is involved where non-flexible conduits are used and possessing the additional advantages of fiexibility, ease in adjustment and facilitating replacement or repair.

In specific construction the flexible coni duit A which I employ is formed from a spirally wound strip of sheet metal vfashioned in cross section to have a convex portion B on one edge thereof, a straightportion C adjacent thereto and an outwardly turned fiange D at the opposite edge. Thus the convex portion' of one convolution overlaps the straight or cylindrical portion of an adjacentconvolution, permltting of a relative sliding movement, whilev the fiange B prevents any disengagement` of said convolutions. The conduit A when completely formed has an external convex thread and an internal concave thread so that two conduits differing in diameter by the gauge of the metal are 'capable of being' joined by screwingpne into the other. In the same manner such conduit can be engaged with any other fitting either by screwing it into internally correspondingly threaded nipple or screwing it upon an externally lthreaded nipple.

As shown in Figure l, two conduit sec. tions A and A vof the same diameter are `joined to each other Aby a similarly threaded sleeve member E, which may be first screwed -socketsG of an outlet fitting H. Figure 5 shows the method of joining a conduit having an installed conductor such as I with a conduit As containing a branch conductor J. For this purpose the conduit A is severed or a portion thereof is cutaway so as to provide access tothe conductor I and permit of splicing the conductor J thereto, as indicated at K.

A two part junction box L having threaded nipples L is then placed over the joint with the threaded nipples engaging thethreads of the conduits. The sections may then be secured to each other by clip members such as M engaged therewith so as to bridge the joint therebetween, as shown in Figure 6. In Figure 8 another form of junction box is illustrated, this being formed of a spirally wound strip having a straight portion N., a flaring portion O and a second straight portion P of larger diameter. The portions N may be screwed onto the ends of the conduit sections to furnish access to the conductor for forming a splice or for any other work to be performed thereon. The two sections may then be screwedon their respective conductors so as to come into engagement with each otherl sections. This bushing ma be either a single section of threaded tu e'of an intermediate diameter. or it may be formed* of a series of said tubes of progressively changing diameter which engage each other and the conduit. Figure 12 shows the condu't A engaging a nipple member S formed either of a spirally wound strip or of an integral pressed metal member having a flange 'i at one end. Such a nipple may be inserted in one of the outlet openings of a conduit outlet box and will form a means of attaching the conduit thereto. Figure 13 shows a cross section for adjacent conduit sections provided with threaded nipples U for engaging coupling sleeves V.

One advantage of coupling conduit sections with a similarly formed spirally wound member is that the couplin as well as the rest of the conduit is ilexib e. This avoids localizingstresses at the joint, which otherwise might cause a bending or a breaking of the conduit.

What I claim as my invention is:

l. A conduit system comprising a plurality of conduit sections each formed of a spirallyy wound strip forming external and internal screw-threads and a coupling for said sections of a similar spirally wound strip of different diameter adapted to be screwed into engagement with the threads formed bythe spiral windings of said sections.

2. A conduit system comprising a plurality of sections each formed of a spirally wound strip forming external and internaliscrew threads, of a coupling for said sections formed of a similar spirally wound strip adapted to be screwed into engagement with the external threads of one and the internal threadsfof another of said sections.

3. A conduit system comprising a conduitsection formed of a s irally wound strip forming a screw threa ed internal and external surface and a conduit section similarly formed but of a different diameter adapted to be screwed into engagement with said first section.

4. A conduit system comprising a plurality of conduit sections each formed of a spirally wound strip formin' screw threaded external and internal sur aces said sections bein of different diameters and a couplin for sai sections formed of a similarly spiralIy wound strip adapted to be screwed into engagement with the external threads of one and the internal threads of the other of said sections.

5. A conduit system comprising a plurality of conduit sections each formed of a spirally wound strip forming screw threaded external and internal surfaces, said sections being of different diameters and a coupling bushing for connecting said sections formed of a similar spirally wound strip of a diameter to form an external threaded engagement with one section and an internal threaded engagement with the other section.

6. A conduit system comprising a plurality of conduit sections each formed ot' a spirally wound strip forming screw threaded internal and external surfaces, said sections being of different diameters permitting of telescopically engaging one with the other and a bushing for secur1n formed of a similar spirally wound strip forming an external screw threaded engagesaid sections to each other ment with the small diameter section and an l ICI 

